Retrobulbar syringe and methods of use

Abstract

A device useful for making retrobulbar injections includes an inner syringe contained within an outer syringe. A spring retained within the outer syringe biases the inner syringe proximally, which a catch mechanism on the two syringes prevents the inner syringe from moving out of the outer syringe. A distal needle on the inner syringe is movable within a distal sheath of the outer syringe, and can be extended beyond the distal end of the sheath to permit the device to piece more resilient tissues, and can be withdrawn by action of the spring within the sheath to protect more delicate tissues from the needle.

I claim: 
     
       1. A retrobulbar syringe comprising:
 an inner syringe having a hollow barrel with a proximal end, a distal end, an outer barrel surface, a plunger in the barrel, and a needle attached to the barrel distal end; 
 an outer syringe having a hollow barrel with a proximal end, a distal end, an barrel inner surface, and a sheath attached to the outer syringe barrel distal end, wherein the inner syringe is at least partially contained in the outer syringe barrel, and wherein the needle is at least partially contained and movable in the sheath; 
 a spring inside the outer syringe barrel bearing against the inner syringe and biasing the inner syringe toward the outer syringe proximal end; 
 a first locking member on the inner syringe barrel outer surface, and a second locking member on the outer syringe barrel inner surface, the first and second locking members being configured and arranged to inhibit the inner syringe from being moved proximally out of the outer syringe barrel; 
 wherein at least one of the first and second locking members comprises a ring extending entirely around the inner syringe barrel or the outer syringe barrel, respectively. 
 
     
     
       2. A retrobulbar syringe according to  claim 1 , wherein the first and second locking members are configured and arranged to prevent the inner syringe from being moved proximally out of the outer syringe barrel. 
     
     
       3. A retrobulbar syringe according to  claim 1 , wherein the first and second locking members are configured and arranged to permit the inner syringe to be pushed distally into the outer syringe barrel with at least a portion of the needle extended distally from the sheath. 
     
     
       4. A retrobulbar syringe according to  claim 1 , wherein the first and second locking members both comprise triangularly shaped, oppositely oriented elements. 
     
     
       5. A retrobulbar syringe according to  claim 1 , wherein both of the first and second locking members comprises a ring extending entirely around the inner syringe barrel or the outer syringe barrel, respectively. 
     
     
       6. A retrobulbar syringe according to  claim 1 , wherein the sheath comprises a proximal portion and a distalmost portion, the hardness of the distalmost portion being less than the hardness of the proximal portion. 
     
     
       7. A method for inserting a needle into a patient's orbit, wherein said needle is contained in a sheath and is moveable in and out of said sheath, the method comprising:
 squeezing two syringes together, the syringes including rings on an outer surface of an inner syringe and on an inner surface of an outer syringe, including causing a distal tip of the needle to extend out of a distal end of the sheath; 
 pushing said syringes, the needle, and the sheath through the patient's skin with at least the distal tip of the needle extending out of the distal end of the sheath; 
 stopping said squeezing and allowing the needle tip to retract inside the sheath; 
 pushing said syringes with the needle further into the orbit with the needle retracted inside the sheath; 
 contacting delicate structures of the orbit with a softer distal end of the sheath; 
 pushing a plunger on an inner syringe of the two syringes and injecting an anesthetic into the orbit; and 
 moving the inner syringe distally away from the sheath a distance sufficient so that the ring on the outer surface of the inner syringe is distal of and trapped distally behind the ring on the inner surface of the outer syringe. 
 
     
     
       8. The method of  claim 7 , wherein said squeezing comprises compressing a spring and causing the inner syringe to move distally and the needle tip to extend out the distal end of the sheath. 
     
     
       9. The method of  claim 7 , wherein said stopping the squeezing comprises expanding the spring and retracting the needle into the sheath. 
     
     
       10. The method of  claim 7 , wherein the rings are triangular in shape and opposite in orientation.